Explain auth logic some more

lib/gitlab/auth.rb

@@ -3,9 +3,11 @@ module Gitlab
     def find(login, password)
       user = User.find_by(email: login) || User.find_by(username: login)
 
+      # If no user is found, or it's an LDAP server, try LDAP.
+      #   LDAP users are only authenticated via LDAP
       if user.nil? || user.ldap_user?
         # Second chance - try LDAP authentication
-        return nil unless ldap_conf.enabled
+        return nil unless Gitlab::LDAP::Config.enabled?
 
         Gitlab::LDAP::User.authenticate(login, password)
       else

spec/lib/gitlab/auth_spec.rb

@@ -28,8 +28,7 @@ describe Gitlab::Auth do
     end
 
     context "with ldap enabled" do
-      before { Gitlab.config.ldap['enabled'] = true }
-      after  { Gitlab.config.ldap['enabled'] = false }
+      before { Gitlab::LDAP::Config.enabled.stub(enabled?: true) }
 
       it "tries to autheticate with db before ldap" do
         expect(Gitlab::LDAP::User).not_to receive(:authenticate)